CVE-2015-2079 is a critical remote code execution vulnerability affecting Usermin versions 0.980 through versions prior to 1.660. Usermin is a web-based user interface for Unix-like systems, commonly used for managing user accounts and system settings. The vulnerability arises from improper neutralization of directives in statically saved code, specifically related to the use of the Perl open function in the uconfig_save.cgi script. The affected code uses the two-argument form of Perl's open function instead of the safer three-argument form, which leads to improper handling of file paths and allows an attacker with limited privileges (requiring low privileges but no user interaction) to inject malicious directives. This injection can lead to arbitrary code execution on the server hosting Usermin. The vulnerability is classified under CWE-96, which concerns improper neutralization of directives in statically saved code, commonly referred to as static code injection. The CVSS v3.1 base score is 9.9, indicating a critical severity level with the vector AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H, meaning the attack can be launched remotely over the network with low attack complexity, requires low privileges but no user interaction, and impacts confidentiality, integrity, and availability with a scope change. Although no known exploits are reported in the wild, the vulnerability's nature and severity make it a high-risk issue for affected systems. The lack of patch links suggests that users must verify the availability of updates from the vendor or consider alternative mitigation strategies.

For European organizations, the impact of this vulnerability can be severe. Usermin is often deployed in enterprise environments, universities, and hosting providers across Europe for user account management and system administration. Exploitation can lead to full system compromise, allowing attackers to execute arbitrary code with the privileges of the Usermin service, potentially escalating to root or administrative access. This can result in data breaches, disruption of services, unauthorized access to sensitive information, and lateral movement within networks. Critical infrastructure operators, government agencies, and enterprises relying on Unix-like systems with Usermin installed are at particular risk. The vulnerability's ability to compromise confidentiality, integrity, and availability simultaneously makes it a significant threat to operational continuity and data protection compliance under regulations such as GDPR. Additionally, the scope change in the CVSS vector indicates that exploitation can affect resources beyond the initially vulnerable component, amplifying the potential damage.

1. Immediate verification of Usermin versions in use: Organizations should inventory their systems to identify Usermin installations and confirm if versions 0.980 through prior to 1.660 are deployed. 2. Apply vendor patches or updates: Although no direct patch links are provided, users should consult the official Usermin project or maintainers for updated versions that address CVE-2015-2079. 3. If patches are unavailable, implement strict access controls: Restrict access to the Usermin web interface to trusted IP addresses or VPN-only access to reduce exposure. 4. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious requests targeting uconfig_save.cgi or attempts to exploit Perl open misuse. 5. Monitor logs for unusual activity related to Usermin, especially attempts to invoke uconfig_save.cgi or anomalous file operations. 6. Consider disabling Usermin if it is not essential or replacing it with alternative management tools that do not have this vulnerability. 7. Conduct regular security assessments and penetration testing focusing on web interfaces and CGI scripts to detect similar injection vulnerabilities. 8. Educate system administrators about the risks of using outdated software and the importance of timely patching, especially for web-facing management tools.